1. Field of the Invention
This invention relates generally to appliances commonly referred to as nutrunners and used in manufacturing for applying and securing nuts to bolts during assembly operations. More particularly, this invention relates to improvements in the drive mechanism and a strain gauge mounting in order to provide improved control of the performance of the appliance.
2. Description of the Prior Art
Prior nutrunner drive apparatus has been characterized by an electrically powered motor having a strain gauge mounted to the motor shaft between the motor and drive gearing of the appliance. This gauge is used to provide an electrical output corresponding to the torque being delivered by the motor. In such nutrunner devices, the gearing is used to alter the direction of the drive to deliver torque at a right angle to the longitudinal axis of the appliance. In these devices, due to frictional losses in the drive mechanism, the torque delivered by the motor and measured by the strain gauge is not the same as the torque ultimately delivered by the appliance to the nut. As a result, control of the motor and the torque delivered to the nut becomes inaccurate.
With the configuration of prior designs, movement of the strain gauge mounting to a location nearer the nut engagement produces interference with the location of the gearing and difficulty in routing wires to the gauge.